In a large frying pan, heat a drizzle of olive oil over medium-high heat. Add the Italian sausage and chopped onion, cooking for 4-5 minutes until the sausage is browned and the onions are soft. Stir in minced garlic and sauté for an additional minute.

Transfer the browned sausage and onion mixture into the slow cooker, ensuring to scrape the pan for all flavorful bits. Add in the low-sodium broth, chopped potatoes, salt, pepper, and crushed red pepper flakes. Stir to mix evenly.

Cover the slow cooker and set it to cook on Low for 4-5 hours or on High for 2 hours.

Once the cooking time is complete and the potatoes are fork-tender, carefully stir in the chopped kale, cream, and freshly grated Parmesan cheese. Cook for an additional 30 minutes.

Before serving, adjust seasonings with additional salt and pepper if needed. Ladle the soup into bowls and enjoy with crusty bread.